Quasiparticle current in ballistic NcS'S junctions

Abstract

Nonstationary properties of ballistic constrictions $Nc{S}^{\prime }S$ with disordered $S^{\prime }S$ electrodes are analyzed theoretically. Amplitudes of Andreev and normal reflections at the constriction are related to the solutions of a stationary Green function problem in an inhomogeneous electrode in a dirty limit. This provides a generalization of the model of Blonder, Tinkham and Klapwijk for a spatially inhomogeneous case. The relation between quasiparticle current in $Nc{S}^{\prime }S$ junctions and energy spectrum of a $S^{\prime }S$ proximity sandwich is found for arbitrary parameters of $S^{\prime }$ and $S$ materials and of interface.

16 pages, RevTex, 4 figures available upon request from [email protected]